Joint construction for runway slabs of prestressed concrete



y 13, 1965 u. FINSTERWALDER 3,

JOINT CONSTRUCTION FOR RUNWAY SLABS OF PRESTRESSED CONCRETE Filed Aug. 24. 1961 2 Sheets-Sheet 1 INVENTOP" UUfIC/ffiA/S/YJWIME? July 13, 1965 u. FINSTERWALDER 3,194,129

JOINT CONSTRUCTION FOR RUNWAY SLABS OF PRESTRESSED CONCRETE Filed Aug. 24, 1961 2 Sheets-Sheet 2 lNVfA/fO/P:

11mm l-Wvsmmmm United States Patent 3,194,129 JUINT CUNSTRUCTION FOR RUNWAY SLABS 6F PRESTRESSED CONRETE Ulrich Finstervvalder, Munich, @hermcnzing, Germany,

assignor to Dycherholi & Widmann Kornmanditgesellschaft, Munich, Germany Filed Aug. 24, 1961, Ser. No. 133,671 Claims priority, application Germany, Aug. 27, 1960, D 34,118 3 Claims. (Cl. 94-8) The invention relates to the construction of runways especially for airports and is particularly concerned with the forming of the transverse joints between the runway slabs of prestressed concrete.

In the construction of runways of concrete the forming of the transverse join-ts that are required between the runway slabs at predetermined distances owing to the movement of the slabs caused by temperature changes are a considerable problem. These joints are always weak places in a runway because moisture can enter them, which together with the changing loads of traffic, can result in uneven settling in the ground. In addition, the abutments of the wheels of vehicles that roll over the joints cause physical destruction of the edges of the joints. The filling of the joints or gaps with bitumen or similar materials does not afford sufiicient protection and, moreover, cannot be employed for aviation traffic runways because the hot gases of the jet planes destroy the material cast into the gaps.

By prestressing the slabs of the runways longitudinally it has been possible to increase the distances between the joints and thus decrease the number of transverse gaps. However, with the increase in the length of the runway sections produced without gaps, also the movement is increased which must be permitted by the gap so that these gaps must have considerable tolerance and must be constructed in a manner similar to bridge construction. In addition, it is necessary that the tension members which extend longitudinally of the runway must also be anchored at the gap and recesses must be provided in the runway slab for engagement by the tension presses for placing the tension members under tension.

It is an object of the invention to provide a simple and satisfactory solution of the problem of forming the transverse joints between the runway slabs of prestressed concrete where above all adequate accommodation of the anchoring means of the longitudinal tension members and an orderly introduction of the tension forces in the concrete may be achieved.

In accordance with the invention casings preferably of cast steel rest against the end surfaces of adjacent runway sections which form the joint which are placed alongside one another and at a distance from one another that corresponds to the width of the gap, where each casing is engaged by at least one tension member of the runway slab while the casings are formed in such a manner that the end wall which is opposite the gap forms the abutment for the tension member or tension members while bridge members establish a connection with the front wall which faces the gap or joint.

In a preferred embodiment of the invention the casings or castings have a T-shaped outline, while that part which extends perpendicularly to the gap has wing portions formed at one end and .on both sides thereof which extend parallel to the gap and which constitute the connection between the tension members and the longitudinal armoring of the runway. This part has further-more a hollow space which is open towards the top in which the tension members are anchored.

The wing portions which form the closure at the end wall of the. runway slab at the joint comprise a small bridge member, which at the surface of the runway merges into a flange that extends away from the gap or joint. In these lateral flanges of the wing portions that confront each other at both sides of the gap recesses are provided, into which is inserted a sliding plate of sheet metal which covers the gap between the casings or castings which is firmly connected to one wing portion, for example, by means of screws and which can freely slide on the other flange or wing portion.

The hollow spaces of the castings or casings may be filled with cement mortar, bitumen or the like, after the full prestressing force has been applied to the tension members and may be covered with suitable steel plates that are connected with the casings.

Further objects and advantageous features of the invention will become apparent from the following specification of an embodiment illustrated in the drawings, in which:

FIG. 1 is a cross-section through two casings or castings which are placed opposite one another, taken along the line I-I of FIG. 3;

FIG. 2 is a cross-section along the line 11-11 of FIG.

3; and

FIG. 3 is a plan view looking downwardly upon FIGS. 1 and 2 with the sliding plate removed.

The joint formation in accordance with the invention is defined by a plurality of casings in the form of castings that are substantially identical, which are arranged on both sides along the joint at a distance from one another corresponding to the width of the gap and which constitute the closure or end of the concrete runway slabs 1, 1'. Each casing is in the fiorm of a hollow element 2, 2' which is box-like and of substantially rectangular shape as seen from the top and which is open at the top and towards the side facing the joint. In the embodiment illustrated the bottom of the hollow element 2, 2' extends at substantially half the height of the thickness of the runway slab and suitably rises slightly toward the gap 6.

On both sides of the forward opening of the hollow element 2, 2 lateral portions 3, 3' are formed at the side walls of the elements. These portions extend in height over the entire thickness of the runway slab and consist of a thin vertical bridge member which engages the front 'wall of the associated runway slab section and is widened at its upper border in the direction away from the joint or gap to form a flange 4, 4'.

At a distance which is sufficiently large to permit the accommodation of the movement caused by temperature changes of the adjacent runway sections, a second casing is placed opposite each of these casings symmetrically with respect to the gap so that the lateral portions or wings consistitute a substantially T-shaped cross-section in the axis of symmetry of which the gap 6 is located. The flanges 4, 4' of the lateral portions or wings 3, 3 are provided at their top with a recess into which a sliding plate 7 may be placed, which is secured on one side of the gap to the flange 4 of a Wing 3, for example, by means of screws 8 and which in accordance with the movements of the runway sections can freely slide on the opposite wing flange 4.

The rear end walls 5, 5' of the hollow elements 2, 2' which are remote from the joint are slightly inclined with respect to the perpendicular and are provided with bores in a manner that at least one tension or tie member 9, 9 may be inserted in the hollow space of the hollow element which is open at the top. The inclination of the end wall 5, 5' as well as that of the bottom of the hollow element 2, 2 corresponds to the inclination of the tension member which is somewhat inclined with respect to the anchoring position, so that the tension press which is inserted in the recesses formed in the hollow elements can be readily applied as the tension members are tensioned.

Patented July 13, 1965 This end wall 5, thus serves as an abutment for the anchoring of the tension member. As shown in FiG. 1, the end walls 5, 5 may also be provided with recesses having ledges 14 adapted to support a platform or cover plate therebetween.

The joint structure in accordance with the invention is installed before the concrete 1, 1 is poured. For this purpose the individual casings or castings are first placed along the gap to be formed and the ends of the longitudinal tension members 9, 9 are inserted through the bores in the rear end walls 5, 5 of the hollow elements 2, 2 into their hollow spaces. Thereupon two of each 7 of the casings that are disposed opposite one another are connected to one another by suitable auxiliary means (not shown) in a manner that between the casings there remains an expansion gap 6, the width of which is made dependent on the air temperature on the day when the concrete is poured. After this the opposite casings which are thus held together in pairs are exactly aligned as to height and direction with respect to the casings which are adjacent in the direction of the gap and the pairs of casings are connected at their adjacent walls by means of straps or yokes 10, 10 of round steel which are welded on. The auxiliary means required for installing the casings are removed after hardening of the concrete.

In order to obtain a good connection of the casings with the surrounding concrete short armoring members 11, 11 of round steel are provided which are welded onto ribs 11a, lla below the hollow elements 2, 2' parallel to the direction of the joint. In addition, transverse tensioning elements 12, 12 which are inserted below the hollow elements 2, 2' insure of good connection between the casings and the concrete therebetween.

Upon hardening of the concrete the prestressing of the longitudinal tensioning elements 9, 9' can be affected at any desired time because the anchoring means of the tensioning elements in the hollow elements 2, 2 which are open at the top are accessible at any time. Upon con pletion of the prestressing the hollow spaces can be filled with cement mortar or bitumen and may be closed with a steel plate that is connected to the casings, for example by means of screws. The gap 6a which still exists in the surface of the runway and which, depending on the prevailing temperature of the runway, is more or less open is defined by the edge of the upper recess of the flange 4 and 4 and the sliding plate 7. It can remain open because its small depth does not constitute any obstacle as the wheels of a vehicle run over it.

The joint construction in accordance with the invention has the advantage that it can be assembled in situ from any desired number of simple components which are substantially identical. The individual components can be placed adjacent one another in a very simple manner until'the required length is attained. Suitably the length of the lateral wings can be adapted to the distance between the longitudinal tension members if a tension member is to be introduced and anchored in each casing. If the prestressing of the runway slab is to be stronger, then it is also possible to accommodate two or more tension members in a casing which is constructed accordingly. The length of the lateral portions 3, 3 can how ever also be adapted to different distances of longitudinal armoring, if such is required for static reasons. The wings 3, 3 are cut off at the edges of the runway to correspond to the width of the runway.

A further advantage is obtained by the joint construction in accordance with the invention in that an additional element at the front ends of the runway slab sections is eliminated because the casings atthe joint serve as a shell. Moreover, the casings are self-supporting and require no elaborate securing during the construction procedure. The casings are preferably made of cast steel which in sures of almost unlimited durability of the joint construction. Moreover, the anchoring of the longitudinal tensioning elements in the recesses that are required for setting up the tension presses is included in the joint construction while the rear Walls of the individual casing serve as an abutment for anchoring the tension members.

The joint construction in accordance with the inventions from individual unitary casings in which the joint formation is combined with the anchoring of the longitudinal tension elements, provides the further advantage that the prestressing force is not only imparted at points by the actual anchoring element in a manner that the force radiates from the tension members so that the regions between the recesses required for placing the tension press would remain without prestressing, but by virtue of the rigid construction of the casings with lateral wings the concrete is prestressed also between the anchoring'of the tension members and the gap to the same or substantially to the same extent as the runway plate itself.

Having now described my invention with reference to the embodiment illustrated in the drawings, I do not wish to be limited thereto, but what I desire to protect by United States Letter Patent is set forth in the appended claims.

I claim:

1. A joint construction for runway slabs, particularly for airport runways of prestressed concrete having runway sections with proximate end portions defining a gap therebetween and including a plurality of structural casings of cast steel or the like disposed along the ends of said sections and coextensive therewith, said casings being arranged in opposed cooperating pairs, with each said casing having a substantially vertically disposed front end wall extending proximate and substantially parallel to the front end wall of the opposite casing of said pair with a space therebetween corresponding to the width of said gap, the front end wall of each said casing having an upper flange extending laterally away from the gap and terminating in a lip extending upwardly to the level of the wearing surface of the slab and defining-an upwardly opening recess proximate the top of and on both sides of said joint and coextensive therewith, a bridging platform in said recess, each said casing being provided with at least one upwardly opening box shaped projection extending rearwardly from the front end wall and away from the joint and terminating in a substantially vertically disposed rear end Wall spaced from said front end wall, said projection of each of said pair of casings defining an upwardly opening trough extending transversely across said pavement joint and at least one longitudinal tension member anchored to said rear end wall of each said casing.

2. Joint construction in accordance with claim 1 wherein said rear end wall of each pair of casings has a recess defining a ledge adjacent the upper end thereof, said trough is filled with concrete or the like to the level of the ledges, and said ledges being adapted to receive a cover plate therebetween.

3. Joint construction in accordance with claim 1 wherein said platform is in the form of a sliding plate anchored on one side of said gap to one said flange and adapted to slide freely on the flange on the other side of said gap.

References Cited hy the Examiner UNlTED STATES PATENTS 1,427,557 8/22 Smith 94-18 1,726,031 8/29 Lathrop 50128 2,029,817 2/36 Fegles 9418 X 2,286,019 6/42 Smith 94-18 2,590,685 3/52 Coif 948 2,632,367 3/53 Martin 9418 2,887,130 5/59 Kell 50129 2,976,782 3/61 Thom 9418 3,022,713 2/62 Friberg 948 X FOREIGN PATENTS 1,026,196 2/53 France.

JACOB L. NACKENOFF, Primary Examiner. 

1. A JOINT CONSTRUCTION FOR RUNAWAY SLABS, PARTICULARLY FOR AIRPORT RUNAWAYS OF PRESTRESSED CONCRETE HAVING RUNAWAY SECTION WITH PROXIMATE END PORTIONS DEFINING A GAP THEREBETWEEN AND INCLUDING A PLURALITY OF STRUCTURAL CASINGS OF CAST STEEL OR THE LIKE DISPOSED ALONG THE ENDS OF SAID SECTIONS AND COEXTENSIVE THEREWITH, SAID CASINGS BEING ARRANGED IN OPPOSED COOPERATING PAIRS, WITH EACH SAID CASING HAVING A SUBSTANTIALLY VERTICALLY DISPOSED FRONT END WALL EXTENDING PROXIMATE AND SUBSTANTIALLY PARALLEL TO THE FRONT END WALL OF THE OPPOSITE CASING OF SAID PAIR WITH A SPACE THEREBETWEEN CORRESPONDING TO THE WIDTH OF SAID GAP, THE FRONT END WALL OF EACH SAID CASING HAVING AN UPPER FLANGE EXTENDING LATERALLY AWAY FROM THE GAP AND TERMINATING IN A LIP EXTENDING UPWARDLY TO THE LEVEL OF THE WEARING SURFACE OF THE SLAB AND DEFINING AN UPWARDLY OPENING RECESS PROXIMATE TO TOP OF AND ON BOTH SIDES OF SAID JOINT AND COEXTENSIVE THEREWITH, A BRIDGING PLATFORM IN SAID RECESS, EACH SAID CASING BEING PROVIDED WITH AT LEAST ONE UPWARDLY OPENING BOX SHAPED PROJECTION EXTENDING REARWARDLY FROM THE FRONT END WALL AND AWAY FROM THE JOINT AND TERMINATING IN A SUBSTANTIALLY VERTICALLY DISPOSED REAR END WALL SPACED FROM SAID FRONT END WALL, SAID PROJECTION OF EACH OF SAID PAIR OF CASINGS DEFINING AN UPWARDLY OPENING TRANSVERSELY ACROSS SAID PAVEMENT JOINT AND AT LEAST ONE LONGITUDINAL TENSION MEMBER ANCHORED TO SAID REAR END WALL OF EACH SAID CASING. 